The IARC Monographs on the Evaluation of Carcinogenic Risks to Humans represent an international expert-consensus approach to carcinogen hazard identification. The long-term objective is to critically review and evaluate the published scientific evidence for all carcinogenic hazards to which humans are exposed. These include chemicals, complex mixtures, occupational exposures, lifestyle factors, and physical and biological agents. National and international health agencies use the IARC Monographs as an authoritative source of scientific information and as the scientific basis for their efforts to control cancer. Each IARC Monograph includes a critical review of the pertinent scientific literature and an evaluation of the weight of the evidence that an agent or exposure may be carcinogenic to humans. Agents are selected for evaluation based on evidence of human exposure and some evidence of carcinogenicity. Agents can be re-evaluated if significant new data become available. The program also collaborates on scientific meetings on mechanisms of carcinogenesis and other topics pertinent to evaluations of carcinogenicity. A written Preamble to each volume of IARC Monographs describes the principles and procedures that are followed, including the scientific criteria that guide the evaluations. Each IARC Monograph is developed by a working group selected on two principles: to invite the best-qualified experts and to avoid real or apparent conflicts of interests. Working groups typically consist of 20-25 scientists from 10-12 countries, with expertise in cancer epidemiology, experimental carcinogenesis, and related disciplines. The working group meets to review and reach consensus on drafts prepared by the experts before the meeting, and to develop and reach consensus on the evaluation. Later, IARC scientists review the text and tables to ensure their scientific accuracy and clarity, and the volume is edited and published. Funds are requested to support two of the three volumes produced each year.